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Railways PYQCBT 1 2016

RRB NTPC · Question 17

If a – b = 5 and a^2 + b^2 = 97, ab = ? A. 48 B. 32 C. 36 D. 72

  1. A

  2. C

  3. B

  4. D

Show answer & explanation

Answer: (B) C

Explanation

(a − b)² = a² + b² − 2ab, so 25 = 97 − 2ab. Then 2ab = 72 and ab = 36.